For the study, 174 Catholic priests, nuns and monks without memory problems had their memory tested yearly for six to 15 years before death. After death, scientists examined their brains for hallmarks of Alzheimer's disease called plaques and tangles.

"In our first study, we used the end of life as a reference point for research on memory decline rather than birth or the start of the study," said study author Robert S. Wilson, PhD, of Rush University Medical Center in Chicago.

The study found that at an average of about two-and-a-half years before death, different memory and thinking abilities tended to decline together at rates that were 8 to 17 times faster than before this terminal period.

Higher levels of plaques and tangles were linked to an earlier onset of this terminal period but not to rate of memory decline during it.

In an accompanying editorial, author Hiroko H. Dodge, PhD, with Oregon Health and Science University in Portland and a member of the American Academy of Neurology, noted, "The findings suggest that the changes in mental abilities during the two to three years before death are not driven directly by processes related to Alzheimer's disease, but instead that the memory and other cognitive decline may involve some biological changes in the brain specific to the end of life. The study by Wilson and his co-authors deepens our understanding of terminal cognitive decline."

The second study, also conducted by Wilson, focused on mental activities and involved 1,076 people with an average age of 80 who were free of dementia. Participants underwent yearly memory exams for about five years. They reported how often they read the newspaper, wrote letters, visited a library and played board games such as chess or checkers. Frequency of these mental activities was rated on a scale of one to five, one meaning once a year or less and five representing every day or almost every day.

The results showed that people's participation in mentally stimulating activities and their mental functioning declined at similar rates over the years. The researchers also found that they could predict participants' level of cognitive functioning by looking at their level of mental activity the year before but that level of cognitive functioning did not predict later mental activity.

"The results suggest a cause and effect relationship: that being mentally active leads to better cognitive health in old age," said Wilson.

The studies were supported by the National Institute on Aging and the Illinois Department of Health.

Note: If no author is given, the source is cited instead.

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